The PoE technology refers to that power is supplied to a terminal by using an Ethernet, which can effectively resolve power supply issues for terminals such as an Internet Protocol (IP) telephone, a portable device charger, a card reader, a camera, and a data collector. For these terminals, cabling of a power system is no longer an issue to be considered, and power is supplied to the devices once they are connected to a network. A PoE system includes PSE and a powered device (PD). The PSE is configured to supply power to the PD.
With the development of PoE technologies and the improvement of PoE standards, more types of devices support remote power supply, and loads of the devices are not completely the same. However, in a PoE-related standard, an output voltage of PSE is generally fixed, for example, 53.5 volts (V). When a line voltage drop is excessively large because of a relatively long network cable or a relatively high transmission power between the PSE and a PD, a voltage received by the PD cannot be satisfactory, which further affects normal working of the PD.